Bacterial Growth (BE #2)

Question 1

Binary fission

Answer 1

asexual reproduction in bacteria

Question 2

How does a bacterial cell ensure that the replicated chromosomes get where they need to to go during cell division?

Answer 2

The duplicated chromosomes attach to separate spots on the plasma membrane & then it divides.

Question 3

Phases of bacterial growth in the lab - define:

lag
log
stationary
death

Answer 3

lag - cell numbers remain constant; cells are preparing to how.

log - cell numbers increase exponentially

stationary - cells become smaller; some produce endospores

death - cell numbers decrease exponentially

Question 4

Why would a bacterial culture enter the stationary phase?

Answer 4

overcrowding; accumulation of waste; depletion of nutrients; pH change

Question 5

Why don’t bacteria go through all the stages in nature the way they do in the lab?

Answer 5

In nature, bacteria are not confined (limited on space); not limited on nutrients, either. They live with other species, so one’s waste may be another’s energy source.

Question 6

strict aerobe

Answer 6

die in the absence of oxygen

Question 7

microaerophiles

Answer 7

like less oxygen & more carbon dioxide

Question 8

facultative anaerobes

Answer 8

can grow in the presence or absence of oxygen; can switch their metabolism

Question 9

aerotolerant anaerobes

Answer 9

don’t use oxygen, but are not killed by exposure to it.

Question 10

obligate (or strict) anaerobes

Answer 10

die in the presence of oxygen

Question 11

Give an example of a mesophilic bacterial species.

Answer 11

Any human pathogen (Staphylococcus aureus, Escherichia coli, Salmonella enterica)

Question 12

mesophilic

Answer 12

human pathogens; like body temperature

Question 13

psychrophilic

Answer 13

bacteria that continue to grow in the refrigerator (cold-loving)

Question 14

thermophilic

Answer 14

bacteria that are not killed by boiling temperatures; endospore formers

Question 15

acidophiles

Answer 15

acid loving - bacteria that grow best at a pH of 1 - 5.4. Ex. Lactobacillus - ferments milk

Question 16

neutrophiles

Answer 16

most human pathogens are in this category; exist from pH 5.4 - 8.5

Question 17

alkaliphiles

Answer 17

base loving - exist from 7.0-11.5;

Ex. Vibrio cholerae (causes cholera)

Question 18

Most bacteria live in ___________ environments.

Answer 18

hypotonic (tonicity)

Bacteria are hypertonic to their environments.

Question 19

halophiles

Answer 19

salt loving - inhabit the oceans

Question 20

indirect measurements of microbes

Answer 20

Measures s property of the mass of cells then estimate the number of microbes.
1. turbidity - look for cloudiness in tube

2. metabolic activity - indicates relative numbers

Question 21

direct measurements of microbes

Answer 21

Give more accurate measurements of #s of microbes:

1. direct counts -
   
   • Coulter Counter - electronic counter; gives total count (living & dead)
     * Direct Microscope Count - special slide w/grid is used to count
2. plate count - bacterial colonies are viewed through a magnifying glass against a Quebec colony-counting grid (give viable count)
3. filtration - liquid or air is drawn through a membrane filter by a vacuum. The pores are too small for microbial cells to pass thru, so they collect on the filter. The filter is then placed on a solid medium & is incubated. (counts viable cells)

Question 22

synthetic medium

Answer 22

is prepared in a lab using precise materials or well-defined materials.

Question 23

complex medium

Answer 23

contains reasonable familiar materials by varies slightly in chemical composition from batch to batch

Question 24

selective media

Answer 24

encourages the growth of some bacteria, but suppresses the growth of others (ex. salt sugar allows for growth of Staphylococcus, but not Streptococcus)

Question 25

differential media

Answer 25

has an ingredient that causes an observable change int he medium when a particular biochemical reaction occurs (ex. a color or pH change)

Question 26

What kind of environment is generated in a candle jar? Describe the conditions concerning O2 & CO2

Answer 26

microaerophilic

flame uses O2 until it goes out, leaving more CO2 than O2.

Question 27

List 2 important components of thioglycollate broth medium.

Answer 27

thioglycollate - binds to O2 to prevent O2 from exerting toxic effects on anaerobes

methylene blue - turns blue when O2 is present; clear when there is no O2

Question 28

Escherichia coli -

Answer 28

facultative anaerobe - can switch

Question 29

Pseudomonas aeruginosa

Answer 29

strict aerobe - needs oxygen

Question 30

Streptococcus pyogenes

Answer 30

microaerophile - less oxygen, more CO2

Question 31

Clostridium botulinum
Clostridium tetani
Clostridium difficile

Answer 31

strict anaerobe

Question 32

Clostridium perfringens

Answer 32

aerotolerant anaerobe

Question 33

What are the chemical reactions that take place in a Brewer anaerobic jar?

Answer 33

H2O + gas pack -> CO2 + H2

H2 + O2 -> H2O

Question 34

Purpose of the streak plate method

Answer 34

to isolate a colony of bacteria